Removal of dissolved gas from ink in an ink jet system

Abstract

In the particular embodiment of a device for removing dissolved gas from ink described in the specification, an elongated ink path leading to an ink jet head is formed between two permeable fluorine-containing membranes. The membranes are backed by air plenums which contain support members to hold the membranes in position. Reduced pressure is applied to the plenums to extract dissolved gas from the ink in the ink path without accumulating scum on the membrane surfaces. Increased pressure can also be applied to the plenums to eject ink from the ink jet head for purging. Within the ink jet head, ink is circulated convectively from the orifice to the deaerating path even when the jet is not jetting ink.

We claim: 
     
       1. A device for removing dissolved gas from ink containing dissolved gas and low-molecular-weight components in an ink jet system while preventing formation of scum comprising a gas-permeable, ink-impermeable fluorine-containing membrane which is permeable to dissolved gas in adjacent ink layer but impermeable to low-molecular-weight components of the ink which tend to form scum on the membrane, means for applying ink containing dissolved gas and low-molecular weight components to one side of the fluorine-containing membrane, and means for applying a reduced gas pressure to the other side of the membrane to cause gas to dissolved in ink to be extracted from the ink through the fluorine-containing membrane while preventing passage of low-molecular-weight ink components. 
     
     
       2. A device according to claim 1 wherein the membrane thickness is within the range from about 0.0005 inch to about 0.050 inch. 
     
     
       3. A device according to claim 1 wherein the fluorine-containing membrane comprises a fluorosilicone material. 
     
     
       4. A device according to claim 3 wherein the membrane thickness is within the range from about 0.003 inch to about 0.012 inch. 
     
     
       5. A device according to claim 1 wherein the fluorine-containing membrane comprises a fluorocarbon material. 
     
     
       6. A device according to claim 5 wherein the membrane thickness is in the range from about 0.0005 to about 0.003 inch. 
     
     
       7. A device according to claim 1 wherein the means for applying reduced gas pressure to the other side of the membrane comprises a vacuum plenum. 
     
     
       8. A method for removing dissolved gas from ink containing dissolved gas and low-molecular-weight components in an ink jet system while preventing formation of scum comprising providing a fluorine-containing gas-permeable, ink-impermeable membrane which is permeable to dissolved air in an adjacent ink layer but impermeable to low-molecular-weight components of ink in the layer, applying ink containing dissolved gas and low-molecular-weight components to one side of the fluorine-containing membrane, and applying reduced gas pressure to the other side of the fluorine-containing membrane to extract dissolved gas from the ink while preventing passage of low-molecular-weight ink components. 
     
     
       9. A method according to claim 8 wherein the fluorine-containing membrane comprises a fluorosilicone material. 
     
     
       10. A method according to claim 8 wherein the fluorine-containing membrane comprises a fluorocarbon material.